CNC-controlled machine tools are well known from the prior art in the most diverse embodiments. CNC (“computerized numerical control”) means that the machine tool is numerically controlled, i.e. by means of a CNC program comprising the CNC control data. The machine tool is equipped with a tool that removes material from the workpiece by machining. The control of the tool is performed by means of a control device on the basis of the CNC control data of the CNC program. This makes it possible to precisely machine a workpiece clamped in the machine tool on the basis of the determined CNC control data.
Today, CNC programs are written with the support of software by means of CAM systems (CAM for “computer-aided manufacturing”). A written CNC program comprises control data that controls an inserted tool in relation to a workpiece clamped in a machine tool along a generated path in order to remove material of the workpiece while the path is being traveled.
The prior art discloses devices and methods for simulating the machining of a virtual workpiece on a virtual machine tool, wherein the machining of the workpiece is visualized in a representation unit (display unit) and a user is able to evaluate the simulation in order to optionally establish or change modifications of the control data for controlling the tool.
Applicant's DE 10 2006 043390 A1 discloses a device and method for simulating a sequence for machining a workpiece on a machine tool for the simulation of sequences on CNC machines. The device comprises storage means for storing machine tool data for creating a virtual image of a machine tool, for storing workpiece data for creating a virtual image of a workpiece and for storing resource data for creating a virtual image of a resource. The data required for creating a realistic image of the machine tool are provided by these means. This does not only include a representation of the tool table and the workpiece but also the possibility to display the clamping situation in detail during the simulation. Furthermore, it is made possible to display the machine tool in different configurations including the workpiece and tool. The corresponding data is supplied to the overall simulation unit by the corresponding means. Thus, a machine tool equipped with a workpiece and tool is virtually available.
EP 0 524 344 A1 discloses a graphically interactive dialogue-oriented programming system for generating programs for controlling the machining process for a CNC machine tool. The dialogue-oriented program makes it easy for the user or operator to change, supplement or newly write control programs for a machine tool by a graphic dialogue guide as simply as possible.
JP 2001 282331 A discloses a tool simulation means suitable to simulate a real tool of a machine tool, the control being changeable for a machining by the tool. The simulation of the machining by the tool is displayed on a monitor.
U.S. Pat. No. 6,584,373 B1 discloses a method for controlling a CNC tool and a control system for controlling a CNC tool for a control in cyclically recurring sequences. The control system comprises a data input unit, a visualization unit, a machine tool check unit and an NC control unit. Here, the NC control unit includes at least one stored NC program for generating a movement sequence for the CNC tool.
The prior art path calculation for a CNC-controlled tool is based on geometric dimensions and orients itself on the intended finished part geometry of the workpiece. Control data is generated such that the material of the workpiece is removed layer by layer by a reciprocating motion of an inserted tool along simple paths until the finished part contour has been achieved. This is also referred to as line-by-line machining.
The machining volume along a machining path (removed material volume per time unit), i.e. the cutting performance of the tool in the material is determined by geometric dimensions. Starting from the blank geometry, a machining path is generated in a CAM system which orients itself on static machining volumes determined in cutting tables when the contour profiles of the workpiece geometry are uncritical, i.e. contour profiles that do not endanger the finished part geometry.
When the finished part contour is approached, only milling paths are generated that remove the remaining material under constant feed with different inserted tools by following the finished part contour. The machining period, that is, the time period required to reach the finished part contour by removing material, starting from the blank, is determined by the programmed feed rates and the determined machining path(s).
In order to reduce the machining period of a workpiece from a blank to a finished part, CAM systems known in the prior art generate one or more paths for a tool which reduce air cutting time. Air cutting time is the time for which a controlled tool is controlled in the machine tool without removing material from a clamped workpiece. Air cutting time occurs, for example, when the tool is guided from one point of the workpiece to another point of the workpiece in order to start a new machining path for removing material, with no material being removed from the workpiece during air cutting time. In contrast thereto, a machining path is a path along which the tool for removing material of the workpiece is controlled, i.e. a tool removes material from the workpiece along a machining path.